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I'm getting a shipping container delivered to my property that weighs about 5000 pounds. Once it's delivered I will need to re-position it. I'm thinking of trying to use a number of cylindrical logs, together with some mechanical advantage to move it. My car has a towing capacity of 1500 pounds, so I'm contemplating getting a 6:1 block and tackle, effectively allowing my car to pull 10,000 pounds. I'm a little iffy on a few points though. What is the actual force that is required to pull a 5000 pound container over rolling logs on grass ( slope will also factor in) I have no idea what the coefficient of friction is here. Does the rope that feeds the pulley have to be able to withstand the full force or just 1/6 of the force? Assuming I need an anchor point, does the anchor point need to hold the full force of the pull? (any suggestions on how I can create an anchor point in a grass field .... was thinking maybe driving a steal pipe down a few feet at an angle). What else am I missing?

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  • $\begingroup$ “The slope will help” - be careful, you may find once the container is on rollers it will move of its own free will and gravity... $\endgroup$ – Solar Mike Dec 25 '17 at 7:21
  • $\begingroup$ Will the logs be sitting on a very solid surface (like concrete). If your ground is soft, the logs will just sink in. If the concrete layer is too thin, it will crack and you will be stuck with logs in the concrete. $\endgroup$ – cup Dec 25 '17 at 11:46
  • $\begingroup$ @Solar Mike actually I have to pull it against the slope, but point taken $\endgroup$ – user379468 Dec 26 '17 at 14:49
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Your Cars towing capacity is considering towing on a highway where you have to be able to accelerate to traffic speed and decelerate safely. Considering you are only moving this off road you should be able to safely pull a load as heavy as you have traction for.If you have a tow hitch already on your vehicle the weakest point is likely to be the chain or cable you use. You will need to exercise extreme caution that should that fail there are no people in the danger zone.

With a block and tackle you distribute the load over the number of lines carrying the load. Easy way to look at it is if there are 3 ropes between the pulleys they share 1/3 the load each but if you have a single rope going from the pulley to the load or the pulling vehicle it will of course have the entire load.

How far are you needing to move this container? If it is more than a short distance you might want to consider paying someone to move it for you.

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    $\begingroup$ And you don’t need an anchor point. Attach one set of pulleys to the car, and the other to the shipping container. If you have three ropes between the pulleys, then to move the container 10 feet, you’ll have to drive the car 30 feet. $\endgroup$ – Mark Dec 25 '17 at 4:00
  • $\begingroup$ @mark not seeing at all how this works with no anchor. $\endgroup$ – agentp Dec 26 '17 at 2:02
  • $\begingroup$ @agentp - Thanks for correcting me - you’re right, he does need an anchor point, but it doesn’t have to hold the full force. $\endgroup$ – Mark Dec 26 '17 at 14:36
  • $\begingroup$ @mark sorry is that a typo? it does or doesn't have to hold the full load ? $\endgroup$ – user379468 Dec 26 '17 at 14:53
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    $\begingroup$ Take the simplest arrangement that has a mechanical advantage. Attach a pulley to the container. Tie one end of the rope to the car, pass it through the pulley, then tie the other end to the anchor beside the car. The anchor takes half the load, the car takes half the load, and the car drives 20 feet to move the container 10 ft. $\endgroup$ – Mark Dec 26 '17 at 21:41

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